Manholes are frequently constructed in roadways or other surfaces to allow access to underground structures such as sanitary and storm sewers and utility conduits. The structure defining a manhole is defined herein to include an underground utility box or catch basin (herein collectively referred to as a “utility box”), which provides an underground space to allow access to sewers, utility conduits and the like. Also included is structure that functions to couple the utility box to a manhole cover while ideally maintaining it flush with the ground.
In order to preserve the structural integrity of a manhole and the surface material surrounding it, and in order to avoid obstruction to traffic, it is necessary for all underground portions of the manhole to be substantially watertight, and for the manhole cover to be supported flush with the ground. Roadways, for example, are occasionally built on inclines. In order to properly align the manhole cover, it is therefore necessary to adjust the angle of the manhole cover while still maintaining a watertight seal between the manhole cover and the structure coupling it to the manhole, and between the manhole and the roadway.
In addition, roadways must be resurfaced from time to time, resulting in a new layer of paving material being deposited on the old. This leaves the cover below the new pavement level, and necessitates an often costly and time-consuming excavation and adjustment of the manhole to accommodate the manhole cover's height to the new level.
An improperly aligned manhole cover may allow surface water to infiltrate the ground under the roadway, which then buckles or collapses around the manhole cover. Seasonal freezing and thawing of infiltrated water causes expansion and contraction of the ground surrounding the manhole, accelerating its degradation. Misaligned manhole covers also increase the decay of surface material in response to loads such as traffic. This effect can be exacerbated by insufficient compaction of the ground surrounding the manhole, leading to areas of weakness which are more prone to failure.
Various adjustable manholes are described in U.S. Pat. No. 3,858,998 (Larsson et al.), U.S. Pat. No. 5,451,119 (Hondulas), U.S. Pat. No. 5,470,172 (Wiedrich), U.S. Pat. No. 6,109,824 (Annes), U.S. Pat. No. 6,371,687 (Heintz et al.), U.S. Pat. No. 6,520,713 (Sondrup), U.S. Pat. No. 6,695,526 (Sondrup), U.S. Pat. No. 6,799,920 (Sondrup) and U.S. Pat. No. 6,955,499 (Sondrup). Nonetheless, there is still a need for improved systems that are easy to install and are operative to support or retain a manhole cover substantially flush with a ground surface.